1. Field of the Invention
The present invention relates to an optical recording medium which allows a user to record information data.
2. Description of the Related Art
Currently, a write-once type DVD (Digital Versatile Disc)-R and a rewritable DVD-RW have been commercially produced as optical recording media.
FIG. 1 is a perspective view illustrating the structure of a recording surface and a cross section of a DVD-R or a DVD-RW (hereinafter simply referred to as the xe2x80x9cDVDxe2x80x9d) before information data is recorded thereon.
As illustrated in FIG. 1, convex (when viewed from the view point of the figure) groove tracks GV and concave (similarly, when viewed from the view point of the figure) land tracks LD are spirally or concentrically formed in alternation on a recording layer R of the DVD. As shown in FIG. 1, the DVD has a trasparent substrate B which attaches to the recording layer R at the substrate""s surface having the groove and land tracks.
The land tracks LD are provided with a plurality of previously formed land prepits LPP for use by a DVD recorder (not shown) as addresses for recognizing particular positions on the groove tracks GV and as a recording timing when the DVD recorder records information data (audio data, video data, and computer data). Each of the land prepit LPP is formed to connect two adjacent groove tracks GV, and its bottom surface (indicated by hatching) is continuous with the bottom surfaces (similarly, indicated by hatching) of associated groove tracks.
For recording information data on the DVD as described above, the DVD recorder irradiates a recording beam to the bottom surfaces of groove tracks GV in accordance with the information data. In this process, heat is conducted over a region of the groove tracks GV irradiated with the recording beam, causing the formation of data pits PT in the heated region as illustrated in FIG. 2. In other words, trains of data pits carrying the information data are formed on the groove tracks GV.
However, when the recording beam from the DVD recorder is irradiated to a position including a land prepit LPP on a groove track GV, a deformed information pit PTX is formed as illustrated in FIG. 2. This is because the heat generated when the recording beam is irradiated also affects a portion of the land prepit LPP.
Thus, when information data is reproduced from the DVD having a recording configuration as illustrated in FIG. 2, waveform distortion occurs particularly in a read signal generated by reading the above-mentioned deformed pit PTX, resulting in a higher read error rate.
The present invention has been made in view of the problem mentioned above, and an object is to provide an optical recording medium which is capable of producing a read signal less waveform distortion when information is reproduced therefrom.
An optical recording medium according to the present invention is formed with information tracks on which data pits carrying information data is to be formed, and prepit tracks previously formed with a plurality of prepits. The information tracks and the prepit tracks are formed adjacent to each other, and at least a bottom part of each of the prepits is formed spaced apart from the information tracks.